Analysis of factors associated with postoperative shoulder balance in Lenke Type 1 adolescent idiopathic scoliosis

OBJECTIVE: To study the factors associated with postoperative shoulder balance in Lenke Type 1 adolescent idiopathic scoliosis (AIS) patients with preoperative right-elevated shoulder after posterior thoracic fusion. METHODS: A total of 34 Lenke Type 1 AIS patients were recruited between October 2006 to October 2008. There were 8 boys and 26 girls with an average age of 15.1 years (range, 12 - 19 years). Posterior thoracic fusion was performed in all the patients. There were 23 cases proximally fused to T4 and 11 cases fused to T5. Pearson's correlation analysis was made between radiographic shoulder height (RSH) at the latest follow-up and preoperative T1 tilt, clavicle angle (CA), coracoids process height (CPH), apical vertebral translation (AVT), RSH, coronal and bending proximal/main thoracic curve (PT and MT) Cobb angle, curve flexibility as well as correction ratio of the MT curve. RESULTS: All patients presented right-elevated shoulder preoperatively, with an mean RSH of (-15.9 ± 5.8) mm. At the latest follow-up, PT curve correction was 44% ± 16%, and MT curve correction was 70% ± 10%. Of the 34 patients with an average postoperative RSH of (0.4 ± 7.9) mm, 32 patients had balanced shoulders, and only 2 patients had mild shoulder imbalance with left-elevated shoulder. The RSH at the latest follow-up was found to be negatively correlated with PT curve flexibility (r = -0.682, P 0.05). CONCLUSIONS: For the Lenke Type 1 AIS patients with preoperative right-elevated shoulder, proximal fusion to T4 or T5 could improve shoulder balance significantly. However, the low PT curve flexibility and overcorrection of MT curve may be associated with postoperative shoulder imbalance in such patients.